/*
 ** Authored by Timothy Gerard Endres
 ** <mailto:time@gjt.org>  
 ** 
 ** This work has been placed into the public domain.
 ** You may use this work in any way and for any purpose you wish.
 **
 ** THIS SOFTWARE IS PROVIDED AS-IS WITHOUT WARRANTY OF ANY KIND,
 ** NOT EVEN THE IMPLIED WARRANTY OF MERCHANTABILITY. THE AUTHOR
 ** OF THIS SOFTWARE, ASSUMES _NO_ RESPONSIBILITY FOR ANY
 ** CONSEQUENCE RESULTING FROM THE USE, MODIFICATION, OR
 ** REDISTRIBUTION OF THIS SOFTWARE. 
 ** 
 */

package com.myJava.file.archive.tar;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;


/**
 * The TarBuffer class implements the tar archive concept
 * of a buffered input stream. This concept goes back to the
 * days of blocked tape drives and special io devices. In the
 * Java universe, the only real function that this class
 * performs is to ensure that files have the correct "block"
 * size, or other tars will complain.
 * <p>
 * You should never have a need to access this class directly.
 * TarBuffers are created by Tar IO Streams.
 *
 * @version $Revision: 1.10 $
 * @author Timothy Gerard Endres,
 *  <a href="mailto:time@gjt.org">time@trustice.com.
 * @see TarArchive
 * 
 * <BR>
 * <BR>CAUTION :
 * <BR>This file has been integrated into Areca.
 * <BR>It is has also possibly been adapted to meet Areca's needs. If such modifications has been made, they are described above.
 * <BR>Thanks to the authors for their work.
 *
 */

public
class		TarBuffer
extends		Object
{
    public static final int		DEFAULT_RCDSIZE = ( 512 );
    public static final int		DEFAULT_BLKSIZE = ( DEFAULT_RCDSIZE * 20 );
    
    private InputStream		inStream;
    private OutputStream	outStream;
    
    private byte[]	blockBuffer;
    private int		currBlkIdx;
    private int		currRecIdx;
    private int		blockSize;
    private int		recordSize;
    private int		recsPerBlock;
    
    private boolean	debug;
    
    
    public
    TarBuffer( InputStream inStream )
    {
        this( inStream, TarBuffer.DEFAULT_BLKSIZE );
    }
    
    public
    TarBuffer( InputStream inStream, int blockSize )
    {
        this( inStream, blockSize, TarBuffer.DEFAULT_RCDSIZE );
    }
    
    public
    TarBuffer( InputStream inStream, int blockSize, int recordSize )
    {
        this.inStream = inStream;
        this.outStream = null;
        this.initialize( blockSize, recordSize );
    }
    
    public
    TarBuffer( OutputStream outStream )
    {
        this( outStream, TarBuffer.DEFAULT_BLKSIZE );
    }
    
    public
    TarBuffer( OutputStream outStream, int blockSize )
    {
        this( outStream, blockSize, TarBuffer.DEFAULT_RCDSIZE );
    }
    
    public
    TarBuffer( OutputStream outStream, int blockSize, int recordSize )
    {
        this.inStream = null;
        this.outStream = outStream;
        this.initialize( blockSize, recordSize );
    }
    
    /**
     * Initialization common to all constructors.
     */
    private void
    initialize( int blockSize, int recordSize )
    {
        this.debug = false;
        this.blockSize = blockSize;
        this.recordSize = recordSize;
        this.recsPerBlock = ( this.blockSize / this.recordSize );
        this.blockBuffer = new byte[ this.blockSize ];
        
        if ( this.inStream != null )
        {
            this.currBlkIdx = -1;
            this.currRecIdx = this.recsPerBlock;
        }
        else
        {
            this.currBlkIdx = 0;
            this.currRecIdx = 0;
        }
    }
    
    /**
     * Get the TAR Buffer's block size. Blocks consist of multiple records.
     */
    public int
    getBlockSize()
    {
        return this.blockSize;
    }
    
    /**
     * Get the TAR Buffer's record size.
     */
    public int
    getRecordSize()
    {
        return this.recordSize;
    }
    
    /**
     * Set the debugging flag for the buffer.
     *
     * @param debug If true, print debugging output.
     */
    public void
    setDebug( boolean debug )
    {
        this.debug = debug;
    }
    
    /**
     * Determine if an archive record indicate End of Archive. End of
     * archive is indicated by a record that consists entirely of null bytes.
     *
     * @param record The record data to check.
     */
    public boolean
    isEOFRecord( byte[] record )
    {
        for ( int i = 0, sz = this.getRecordSize() ; i < sz ; ++i )
            if ( record[i] != 0 )
                return false;
            
        return true;
    }
    
    /**
     * Skip over a record on the input stream.
     */
    
    public void
    skipRecord()
    throws IOException
    {
        if ( this.debug )
        {
            System.err.println
            ( "SkipRecord: recIdx = " + this.currRecIdx
                    + " blkIdx = " + this.currBlkIdx );
        }
        
        if ( this.inStream == null )
            throw new IOException
            ( "reading (via skip) from an output buffer" );
        
        if ( this.currRecIdx >= this.recsPerBlock )
        {
            if ( ! this.readBlock() )
                return; // UNDONE
        }
        
        this.currRecIdx++;
    }
    
    /**
     * Read a record from the input stream and return the data.
     *
     * @return The record data.
     */
    
    public byte[]
                readRecord()
    throws IOException
    {
        if ( this.debug )
        {
            System.err.println
            ( "ReadRecord: recIdx = " + this.currRecIdx
                    + " blkIdx = " + this.currBlkIdx );
        }
        
        if ( this.inStream == null )
            throw new IOException
            ( "reading from an output buffer" );
        
        if ( this.currRecIdx >= this.recsPerBlock )
        {
            if ( ! this.readBlock() )
                return null;
        }
        
        byte[] result = new byte[ this.recordSize ];
        
        System.arraycopy(
                this.blockBuffer, (this.currRecIdx * this.recordSize),
                result, 0, this.recordSize );
        
        this.currRecIdx++;
        
        return result;
    }
    
    /**
     * @return false if End-Of-File, else true
     */
    
    private boolean
    readBlock()
    throws IOException
    {
        if ( this.debug )
        {
            System.err.println
            ( "ReadBlock: blkIdx = " + this.currBlkIdx );
        }
        
        if ( this.inStream == null )
            throw new IOException
            ( "reading from an output buffer" );
        
        this.currRecIdx = 0;
        
        int offset = 0;
        int bytesNeeded = this.blockSize;
        for ( ; bytesNeeded > 0 ; )
        {
            long numBytes =
                this.inStream.read
                ( this.blockBuffer, offset, bytesNeeded );
            
            //
            // NOTE
            // We have fit EOF, and the block is not full!
            //
            // This is a broken archive. It does not follow the standard
            // blocking algorithm. However, because we are generous, and
            // it requires little effort, we will simply ignore the error
            // and continue as if the entire block were read. This does
            // not appear to break anything upstream. We used to return
            // false in this case.
            //
            // Thanks to 'Yohann.Roussel@alcatel.fr' for this fix.
            //
            
            if ( numBytes == -1 )
                break;
            
            offset += numBytes;
            bytesNeeded -= numBytes;
            if ( numBytes != this.blockSize )
            {
                if ( this.debug )
                {
                    System.err.println
                    ( "ReadBlock: INCOMPLETE READ " + numBytes
                            + " of " + this.blockSize + " bytes read." );
                }
            }
        }
        
        this.currBlkIdx++;
        
        return true;
    }
    
    /**
     * Get the current block number, zero based.
     *
     * @return The current zero based block number.
     */
    public int
    getCurrentBlockNum()
    {
        return this.currBlkIdx;
    }
    
    /**
     * Get the current record number, within the current block, zero based.
     * Thus, current offset = (currentBlockNum * recsPerBlk) + currentRecNum.
     *
     * @return The current zero based record number.
     */
    public int
    getCurrentRecordNum()
    {
        return this.currRecIdx - 1;
    }
    
    /**
     * Write an archive record to the archive.
     *
     * @param record The record data to write to the archive.
     */
    
    public void
    writeRecord( byte[] record )
    throws IOException
    {
        if ( this.debug )
        {
            System.err.println
            ( "WriteRecord: recIdx = " + this.currRecIdx
                    + " blkIdx = " + this.currBlkIdx );
        }
        
        if ( this.outStream == null )
            throw new IOException
            ( "writing to an input buffer" );
        
        if ( record.length != this.recordSize )
            throw new IOException
            ( "record to write has length '" + record.length
                    + "' which is not the record size of '"
                    + this.recordSize + "'" );
        
        if ( this.currRecIdx >= this.recsPerBlock )
        {
            this.writeBlock();
        }
        
        System.arraycopy(
                record, 0,
                this.blockBuffer, (this.currRecIdx * this.recordSize),
                this.recordSize );
        
        this.currRecIdx++;
    }
    
    /**
     * Write an archive record to the archive, where the record may be
     * inside of a larger array buffer. The buffer must be "offset plus
     * record size" long.
     *
     * @param buf The buffer containing the record data to write.
     * @param offset The offset of the record data within buf.
     */
    
    public void
    writeRecord( byte[] buf, int offset )
    throws IOException
    {
        if ( this.debug )
        {
            System.err.println
            ( "WriteRecord: recIdx = " + this.currRecIdx
                    + " blkIdx = " + this.currBlkIdx );
        }
        
        if ( this.outStream == null )
            throw new IOException
            ( "writing to an input buffer" );
        
        if ( (offset + this.recordSize) > buf.length )
            throw new IOException
            ( "record has length '" + buf.length
                    + "' with offset '" + offset
                    + "' which is less than the record size of '"
                    + this.recordSize + "'" );
        
        if ( this.currRecIdx >= this.recsPerBlock )
        {
            this.writeBlock();
        }
        
        System.arraycopy(
                buf, offset,
                this.blockBuffer, (this.currRecIdx * this.recordSize),
                this.recordSize );
        
        this.currRecIdx++;
    }
    
    /**
     * Write a TarBuffer block to the archive.
     */
    private void
    writeBlock()
    throws IOException
    {
        if ( this.debug )
        {
            System.err.println
            ( "WriteBlock: blkIdx = " + this.currBlkIdx );
        }
        
        if ( this.outStream == null )
            throw new IOException
            ( "writing to an input buffer" );
        
        this.outStream.write( this.blockBuffer, 0, this.blockSize );
        this.outStream.flush();
        
        this.currRecIdx = 0;
        this.currBlkIdx++;
    }
    
    /**
     * Flush the current data block if it has any data in it.
     */
    
    private void
    flushBlock()
    throws IOException
    {
        if ( this.debug )
        {
            System.err.println( "TarBuffer.flushBlock() called." );
        }
        
        if ( this.outStream == null )
            throw new IOException
            ( "writing to an input buffer" );
        
        // Thanks to 'Todd Kofford <tkofford@bigfoot.com>' for this patch.
        // Use a buffer initialized with 0s to initialize everything in the
        // blockBuffer after the last current, complete record. This prevents
        // any previous data that might have previously existed in the
        // blockBuffer from being written to the file.
        
        if ( this.currRecIdx > 0 )
        {
            int offset = this.currRecIdx * this.recordSize;
            byte[]	zeroBuffer = new byte[ this.blockSize - offset ];
            
            System.arraycopy
            ( zeroBuffer, 0, this.blockBuffer, offset, zeroBuffer.length );
            
            this.writeBlock();
        }
    }
    
    /**
     * Close the TarBuffer. If this is an output buffer, also flush the
     * current block before closing.
     */
    public void
    close()
    throws IOException
    {
        if ( this.debug )
        {
            System.err.println( "TarBuffer.closeBuffer()." );
        }
        
        if ( this.outStream != null )
        {
            this.flushBlock();
            
            if ( this.outStream != System.out
                    && this.outStream != System.err )
            {
                this.outStream.close();
                this.outStream = null;
            }
        }
        else if ( this.inStream != null )
        {
            if ( this.inStream != System.in )
            {
                this.inStream.close();
                this.inStream = null;
            }
        }
    }
    
}
